res_query() is rejecting T_ANY and T_CNAME requests since they give answers
with a different type. It also doesn't reject them cleanly, returning the
length of the packet that would be returned (but not filling in the buffer)
instead of -1.
This commit fixes that by allowing T_ANY questions to have any type of answer
and T_A or T_AAAA questions to have T_CNAME answers.
It also returns -1 if it otherwise rejects the response.
See https://bugs.busybox.net/show_bug.cgi?id=5342 which has a test case for
this.
Patch has been tested on OpenWrt and i386 buildroot.
Signed-off-by: Chris Luke <chr...@flirble.org>
---
libc/inet/resolv.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/libc/inet/resolv.c b/libc/inet/resolv.c
index e9f550b..06af2dc 100644
--- a/libc/inet/resolv.c
+++ b/libc/inet/resolv.c
@@ -3736,10 +3736,16 @@ int res_query(const char *dname, int class, int type,
free(a.dotted);
- if (a.atype == type) { /* CNAME */
+ /* Copy the answer only if the type asked for is the same as the answer,
+ * we asked for T_ANY, or an A or AAAA returned a CNAME first.
+ */
+ if (a.atype == type || type == T_ANY || (a.atype == T_CNAME && (type ==
T_A || type == T_AAAA))) {
if (i > anslen)
i = anslen;
memcpy(answer, packet, i);
+ } else {
+ h_errno = NO_DATA;
+ i = -1;
}
free(packet);
return i;
--
1.7.9.5
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